Field of the Invention
The aspect of the embodiments relates to a technique for executing gradation processing on at least one image from among a plurality of images displayed on a plurality of display units.
Description of the Related Art
In recent years, a technique known as “mixed reality (MR)” has been known as a technique for seamlessly combining a real world and a virtual world. There has been known an MR technique using a video see-through head-mounted display (HMD). In the above technique, an object image which substantially conforms to an object observed from a position of the pupil of a user who wears an HMD is captured by a camera. Then, the captured image on which a computer graphics (CG) is superimposed and displayed is displayed on a display device such as a liquid crystal display or an organic electroluminescence (EL) display, so that the user who wears the HMD can observe the displayed image.
In order to enable the user to naturally conduct observation with an increased sense of presence, an image display apparatus used for the HMD displays a wide-angle image. There is provided an image display apparatus using a technique for achieving display of a wide-angle image. In the technique, images having different view angles are displayed as a right-eye image and a left-eye image, and only a part of the right-eye and the left-eye view angles are overlapped with each other, so that the user can observe an image with a view angle wider than in a case of displaying images with the same view angle as the right-eye image and the left-eye image.
However, when the images with different view angles are displayed with respect to the right and the left eyes while only a part of the right-eye and the left-eye view angles are overlapped with each other, there arises a phenomenon in which a boundary portion between a monocular region and a binocular region becomes noticeable, and thus the user cannot naturally conduct observation. This phenomenon arises when a black portion such as a non-display portion of a panel is visually recognized although the image is visible on only one side of the eyes because of the binocular rivalry between the right and the left eyes.
With respect to the above-described phenomenon, Japanese Patent Application Laid-Open No. 2003-337299 discusses a technique for making a black portion unnoticeable by lowering the luminance of an image displayed on an HMD apparatus from a predetermined position at a predetermined lowering rate.
In the technique described in Japanese Patent Application Laid-Open No. 2003-337299, linear gradation is executed to make the black portion unnoticeable, and a boundary portion of the gradation has a rectilinear shape. On the contrary, with respect to an actual image visually recognized by the eyes of a person who does not wear the HMD, the black portion does not provide a sense of discomfort, and the image can be observed as a wide-angle image although a boundary portion between the monocular region and the binocular region also exists. In other words, in order to make the black portion of the gradation unnoticeable as much as possible, a flexible configuration capable of making a shape of a gradation boundary portion close to a shape of the boundary portion actually seen by the human eyes is provided.